Doctor process



- ferred for reasonsof cost.

DOCTOR PROCESS No Drawing. Application April 16, 1954, Serial-No. 423,840

4-Claims; crisis-3st This invention relates to the treatment of sour hydrocarbon oils bythe doctor process. More particularly, it relatesto an improvement in-conventional doctor sweeteningof hydrocarbon oils.

Hydrocarbon oils whichhave been sweetened by the doctor process have a burning quality and oxidation stability lower than that of the oil prior to the sweetening operation. It is an objectofthis invention to improve the burningquality of oils sweetened. by the doctor process. Another object is to improve the oxidation. stability of hydrocarbon oils sweetened by the doctor process. Still another object is to decrease the loss in octane number of naphthas which have been sweetened'by the. doctor process.

These objects and otherobjects, which will be apparent in the course of the detailed description, have been atoms, for example, .octylamine, decylamine, laurylamine,

cetylamine, sterylarnine; (11) secondary aliphatic amines containing' at leastS carbon atoms in eachaliphatic group,

for. example, 'di-n amylamine, di-isoamylamine, and di octylamine; (0.) tertiary aliphatic amine containing at least-'3 carbon atoms ineach aliphatic group, for.ex-

ample, tri-n-propylamine, tri-isopropylamine,. tri-n-butyl amine, trij-isobutylamine, 'tri-n-amylamine, tr'iiisoamyl amine, and tri-octylamine; The tertiary'aliphatic amines do not react with. freelsulfur to formhydrogen sulfide.

Since free sulfur is" presentin the sweet oil in virtually all doctorsweetening operations, the tertiaryaliphatic amines V are the preferred amines. The tri-n-butylamines are pre- At leastan amount of the aliphatic amine mustbepre'sent in the oil to improve the'quality of said oil. In general, at' least about 0.001 weight percent, basedon. oil,- 1 of the aliphatic amine should be present. Amounts up to about Weight percent may be utilized. These large amounts are particularly suitable when extremely refractory oils are beingtreated; andwhen'the aliphatic amine is recoveredv from the sweet'oil by treating. the oil with an acid that is reactivewith the amine to form an oil insoluble salt; This salt may bedecomposed by treatment aliphaticamine." a

The aliphatic amine may be added to the sour oilprio'r to the addition of doctor solution, orthe aliphatic amine -may be added to the mixture of sour oil and doctor solution, In any case, the aliphatic amine must be present in the sour oil prior tooontactirig the sour-oil with free 2,773,010 Patented Dec. 4, 1956 sulfur. sour oil prior to commencing the sweetening operation.

The feed to this process may be any hydrocarbon oil which sour to the'doctor test or has a mercaptan'(copper) numberof atleast about 1.

The process is particularly suitable for the treatment 7 of petroleum distillatesjboiling below about 750 F. Ex-

amples of these distillatesare industrial naphthas, kerosene, diesel'oil, heater oil, gas oil, etc. The process may be used on distillates obtained. by thefractional distillation of crudepetroleum or' on distillates obtained from 7 various conversion processes such as thermal cracking, catalytic cracking, reforming in the presence of hydrogen, etc. Sour. petroleum distillates boiling in the heavier-than e. g., a heater oil boiling between about 330 and 575 are a particularly suitable feed. 1 In the doctor process, the doctor solution is made 11 of an aqueous solutionof an alkali metal hydroxide and i the reaction product of litharge and the alkali metal hydroxide. The amount of free-alkali metalhydroxide pres fresh doctor solution is usually between about 1.5 and 25 grams of PbO per 100 cc. of solution.

are contacted in conventional doctor treating are between about 60 and'175 F. The treating temperature may be determined by the flash point of the particular sour oil charged to the process. Thus, when operating with naphthas,,temperatures on the order of 70 F. may be used;

when operating with a kerosene, temperatures between.

about 90 and"l10' F. may be used; and when operating may be-used.- Still another limitation on the contacting temperature may be color formation in the oil, e. g., some kerosenes rapidly develop color bodies when exposed forI prolonged times at temperatures above about 120 F.

I Free sulfur is added to the contacting'zone to effect the sweetening. Frequently more than the theoretical quantity of 0.5 mol, per each mol of mercaptan sulfur not limit the scope of usefulness of the process. I

present in the sour oil is needed. The use of the theoreticalquantity of free sulfur does not'always produce an oil that is sweet to the doctor 'testf'this is particularly 7 true with heavier-than-gasoline distillates. The amount of.

excess freesulfur necessary varies with thesour'oil charged and the operating conditions. In general, thehigher boiling'thesour oil, the more excess sulfur that is needed oxygen is introduced into the. sweetening zone. The... presence of. free oxygen has a favorable elTecton-Jthe usage of free sulfur and. also helps to convert'some of;

=the PbS formed in the sv/eeteningreaction to the soluble pinmbite formed,

The, results.obtainablej with theprocess are illustrated by -.the followingwoiking;examples It is ,tofbe und stood that these" examples are illustrative only and IIn this examplathe sour oil was athermallycracked heavy naphtha boiling between about 200 and 390 .1?

andhada CFR-Roctane number of 72:3clear.

It is preferred to add the' aliphatic amine to the i ponent alone.

given for the final turbo-jet fuel blend even though only r 4 volume percent of fresh doctor solution containing 1.8 grams of PbO per 100 cc. of solution. The free-sulfur usage was the theoretical requirement. The sour oil, doctor solution and free-sulfur were agitateduntil the oil was sweet. The sweet oil was decanted from the lower layer of doctor solution and water washed to remove entrained doctor solution. The sweet oil was freed of water by passage through a filter paper coalescer. This oil was sweet to the doctor test. s 7

Test 2.Another portion of the sour. oil was contacted according to the'procedure described above except that 0.01 weight percent, based on sour oil, of tri-n-butylamine was added to the sour oil prior to contacting with the doctor solution and free sulfur.

The octane number of the sweet oil derived by the two methods of treating were determined by the CFR-R 'method and also on samples containing 1.0 cc. and 3.0 cc.

respectively of commercial tetraethyllead solution. The

results of these tests are set out below:

Octane Number OFR-R Sweet Oil Clear 1.0 cc. 3.0 cc.

From Test 1 70. 9 77. 7 83 3 From Test 2- 71. 8 78. 84. 4

Example B The effect of aliphatic amine addition was studied on the production of a turbo-jet fuel. This fuel consists of a blend of a cracked light naphtha, 12 volume percent, and a very high end-point virgin heavy naphtha, 88 vol-. ume percent. Only the virgin heavy naphtha fraction is doctor sweetened. The blend of heavy naphtha and light naphtha is more susceptible to oxidation than either com- Therefore, the results of these tests are the virgin heavy naphtha portion is doctor sweetened by either the conventional process or the aliphatic aminedoctor process of this invention.

The two components of the jet fuel have the'following characteristics:

Accelerated Blend Containing Sweet Oil Frornum (16 hours) These tests show that the presence of tri-butylamine in the sour oil prior to doctor sweetening decreased the gum produced in this test by more than one-half over conventional doctor sweetening. Tri-butylamine is not in itself an antioxidant as is shown by the results of test 5. Apparently, the tri-butylamine is eifective only when present in the oil during the doctor sweetening process itself.

Example C In this example, the effect of the process of this invention on burning quality of a heater oil was determined.

' The sour oil charged to the sweetening operation was Virgin Heavy Lig t Naphtha Naphtha Test 3.-In this test, the virgin heavy naphtha was sweetened in accordance with the process set out in test- 1 above, using 34% excess free sulfur.

Test 4.-In this test, the virgin heavy naphtha was sweetened in accordance with the procedure of test 3,-

except that 0.01 weight percent of tri-n-butylamine was added to the sour naphtha prior to the sweetening operation. a

in accordance with the procedure of test 3 except that 0.01 weight percent of tri-n-butylamine was added to the sweet oil after completion of the sweetening operation.

The sweet virgin heavy naphtha obtainedaccording'to the procedures of tests 3-5 was blended with'the cracked Test 5.--In this test, thesour naphtha was sweetened derived by distillation from a high sulfur crude. This heater oil boiled over the range of 330 and 560 F. and had a mercaptan number of 64.

7 Test 6.--In this test, the sour oil was contacted with 5 volume percent of doctor solution at 120 F. in the presenceof 70% of excess freesulfur. Air was used to agitate 'the oil-doctor. mixture. The sweet oil was recovered according to the procedure of test 1.

7 Test 7.In this test, the sweetening was carried out in accordance with the procedure of test 6 except that 0.01 weight percent of tri-n-butylarnine was added to the sour oil before the doctor sweetening operation.

Test '8.This test was carried out in accordance with the procedure of test 6- and 0.01 weight percent of trin-butylamine was added to the sweet oil.

It has been found that sleeve-type burners indomestic heating'installations are most markedly affected by'the presence of deposits formed during the burning of the oil. The Jungers burner is an example of an extremely sensitive sleeve-type burner. Because of this sensitivity the Iungers burner has been adopted by'many refiners as a standard test burner for determining the burning quality of domestic heating oils. A full scale test using the Jungers burner involves the burning of many gallons of oil and many days of operation. A simplerlaboratory procedure has been developed which adequately predicts the results obtainable in the full size Jungers burner test. This laboratory method is known as the steel dish deposit test or steel dish gum test.

' adjusted to maintain the dish at about 500 F. In order to more closely simulate the Iungers burner operation, theoil to be tested is aged in an open vessel at 200 F. for 72 hours. The oil to be tested is dripped at a substantially constant rate onto the dish. The rate of evaporation of the oil from the dish should be substantially equal to the rate of addition of the oilto the dish, i. e., the dish always contains a film of liquid oil. A 400 ml.

ML.* 4 4.4 U 444 Sweet Oil From Steel Dish Deposit, mg.

Test 6 49 Test 7 20 Test 8 46 These tests show that the tri-butylamine is not in itself an inhibitor of deposit formation. However, when the tri-butylamine is present in the oil during the doctor sweetening procedure, the deposit forming tendency of the sweet oil is decreased by more than one-half.

Example D In this example, the raw heater oil of Example C was sweetened according to the procedure described there except that 0.01 weight percent of diphenylamine was added to the sour oil before sweetening. The steel dish deposit of the sweet oil was 48 mg, which shows the diphenylamine was completely ineffective.

sisting of (a) primary aliphatic amines containing at I least 8 carbon atoms, (b) secondary aliphatic amines containing at least 5 carbon atoms in each aliphatic group and (c) tertiary aliphatic amines containing at least 3 carbon atoms in each aliphatic group, (2) contacting said amine-containing sour oil with doctor solution and with free sulfur in an amount at least suflicient to sweeten said distillate, and (3) separating an essentially sweet amine-containing distillate from doctor solution.

2. The process of claim 1 wherein said sour distillate is a naphtha.

3. The process of claim 1 wherein said sour distillate is a heater oil.

4. The process of claim 1 wherein said amine is trin-butylamine.

References Cited in the file of this patent UNITED STATES PATENTS 2,125,636 Holland Aug. 2, 1938 2,311,328 Brower et a1 Feb. 16, 1943 2,366,545 Morris Jan. 2, 1945 2,411,083 Davis et al Nov. 12, 1946 

1. A DOCTOR SWEETENING PROCESS WHICH COMPRISES (1) ADDING TO A SOUR PETROLEUM DISTILLATE BOILING BELOW ABOUT 750* F. BETWEEN ABOUT 0.001 AND 0.1 WEIGHT PERCENT OF AT LEAST ONE ALIPHATIC AMINE SELECTED FROM THE CLASS CONSISTING OF (A) PRIMARY ALIPHATIC AMINES CONTAINING AT LEAST 8 CARBON ATOMS, (B) SECONDARY ALIPHATIC AMINES CONTAINING AT LEAST 5 CARBON ATOMS IN EACH ALIPHATIC GROUP AND (C) TERTIARY ALIPHATIC AMINES CONTAINING AT LEAST 3 CARBON ATOMS IN EACH ALIPHATIC GROUP, (2) CONTACTING SAID AMINE-CONTAINING SOUR OIL WITH DOCTOR SOLUTION AND WITH FREE SULFUR IN AN AMOUNT AT LEAST SUFFICIENT TO SWEETEN SAID DISTILLATE, AND (3) SEPARATING AN ESSENTIALLY SWEET AMINE-CONTAINING DISTILLATE FROM DOCTOR SOLUTION. 